REWINDING MACHINE AND METHOD FOR THE FORMATION OF LOGS OF WEB MATERIAL WITH MEANS FOR SEVERING THE WEB MATERIAL

Abstract: The rewinding machine for the formation of logs (L) of web material (N) wound on a core (A), includes a first winder roller (15) around which the web material (N) is fed, and a second winder roller (17) forming, with the first winder roller, a nip (19) through which the core (A) and the web material (N) pass. A web material-severing device (43) cooperates with the first roller (15). Located upstream of the nip (19), with respect to the direction of movement of the web material (N), is a surface (33) defining, with the roller (15), a channel (39) into which the core (A) is inserted. A conveyor (47; 57; 67) introduces a core into the channel (39). The material-severing device (43) cooperates with the roller (15) along the channel (39) between the region of insertion of a new core and the nip (19).

Description: DESCRIPTION REWINDING MACHINE AND METHOD FOR THE FORMATION OF LOGS OF WEB MATERIAL WITH MEANS FOR SEVERING THE WEB MATERIAL Technical field The invention refers to a surface rewinding machine and method for the formation of logs or rolls of web material wound on a central core. Such rewinding machines are well-known, described, for example, in U.S. Patents No. 4,487,377; 4,723,724; and 4,828,195; and U.K. Patent No. 2,105,688. More in particular, the present invention refers to a rewinding machine which includes a first winder roller on which the web material is fed; a second winder roller defining, with the first winder roller, a nip through which the core and the web material pass; means for feeding the web material to said nip; means for introducing a core on which the web material is to be wound; and a web material severing means cooperating with said first winder roller. Background art A rewinder of this type is described, for example, in U.S. Patent 4,487,377. These rewinders are used for producing smaller-diameter logs or rolls of web material from large-diameter parent rolls. Typically, these machines are used in the paper converting industry to produce rolls of toilet paper, kitchen towels, all-purpose wipers and the like. The formed logs may be as long as 350 cm and only 10-15 cm in outer diameter, and are subsequently cut transversely to their axis to obtain small rolls which may be only 10-30 cm long. In the production of such logs, it is important to use reliable machines able to run at high production speeds (in the range of 600-1000 m/minute) which provide a consistently high-quality product, with uniform windings, especially of the first loops. The length of the material on each log must be presetable and maintained, from log-to-log, with great accuracy. One way to obtain high production rates and a high quality of the manufactured product is shown in U.S. Patent 4,487,377, which provides for a web-cutting member which cooperates with the first winder roller of the rewinder. The web material is cut upstream of the point where the core is introduced. After cutting, the leading edge of the web material adheres to the surface of the winder roller and is transferred (by the rotation of the latter) towards the winding region where the leading edge is made to adhere to a new core suitably introduced by an insertion means. This machine requires means (for holding the leading edge of the web material onto the winder roller) which are housed inside the winder roller and which must be timely activated and deactivated to hold and release the edge at preset moments, thereby allowing the starting of the winding on a new core. Objects of the invention A first object of the present invention is a rewinding machine which is able to produce a high-quality finished product at high speeds with a simpler and more economical construction than that of known rewi ders. A further object of the present invention is to provide a versatile rewinder able to produce logs of varying length without requiring complex mechanisms for adaptation to different lengths of web material without a slipping of the web material on the winder roller onto which it is fed. Another object of the present invention is the construction of a rewinder having means for tearing or cutting the web material, which means are reliable, simple, and inexpensive to produce and maintain. These and further objects and advantages will appear evident to those skilled in the art by a reading of the following description. Disclosure of the invention In the rewinder according to the present invention, a surface or track is provided upstream of the nip between the winder rollers, which defines, together with the web feeding means which feeds the web material into the nip, a channel into which the core is introduced. A web-severing means cooperates with said web feeding means at an intermediate position along said channel between the region of insertion of the new core and the nip defined between the winder rollers. According to the invention, a machine is provided wherein a core is inserted into a channel upstream of the nip between a first and a second winder roller. The web material is severed downstream of the core insertion region by severing means which cooperate with the first winder roller or other means for feeding the material into the nip. This avoids the need of accelerating one of the winder rollers, and the severed web material begins to wind up on the core while the core starts to roll into the channel and on the surface or track by the rotation of the first winder roller. In some cases, the web-feeding means may be a belt system combined with said first winder roller. This arrangement allows a precise severance of the web material to be carried out by severing means which cooperate with the first winder roller, without having to hold the leading edge of the web material on the winder roller, inasmuch as at the moment of severance of the web material, the new core is already in contact with the web material. Furthermore, the un-tensioning of the web material upstream of the winding region is substantially eliminated. If desired, the start of the winding of the web material around the core may be assisted by placing glue on the surface of said core, or by suitable air jet or vacuum or mechanical means. The use of glue ensures a more reliable operation and increases the quality of the final product . The surface or track for the rolling of the core extends, substantially, from the position where the introduction means discharges the core, up to the nip between the two winder rollers. To make the transit of the core from the non-moving surface or track to the second rotating winder roller easier, said surface is preferably comb-shaped, at least in the terminal portion thereof. This comb-like terminal portion cooperates with annular slots in the second winder roller to allow the core, having the first turns of web material wound thereon, to be transferred smoothly and without shocks or strains to the nip between the winder rollers. In practice, since the extension of the track surface on which the core rolls (prior to the insertion thereof into the nip) is relatively short, and the web material very thin, any increase in diameter due to the winding of the first turns is insignificant. Accordingly, the track or fixed surface can define, together with the cylindrical surface of the first winder roller, a channel of substantially uniform cross-section and, advantageously, of a height slightly lower than the diameter of the core. The difference between the height of the channel and the diameter of the core causes the latter to be slightly squeezed when initially inserted thereinto, and this advantageously allows the web material to adhere to the core while facilitating the rotational acceleration of said core. In practice, the severing means are so constructed as to be able to move along a cylindrical path which is almost tangent to the cylindrical surface of the first winder roller, or slightly interfering therewith. The peripheral speed of the cylindrical surface of the first winder roller and of the web material carried thereon is higher than the tangential speed of the severing means along said path. In this way, when the web material is pinched between the severing means and the cylindrical surface of the first winder roller, the difference in speed causes a slight retardation of the web material and thus the tearing thereof. The rotational speed of the unit which carries the severing means is precisely controlled. Perforation lines on the web material adjacent the severing means will facilitate the tearing of the web material. In order for the severing means to enter in contact with the web on the cylindrical surface of the first winder roller at an intermediate position along the said channel, (while the rotary unit carrying the severing means is arranged outside the channel) , the severing means pass through slots or apertures in said track. Thus, by controlling the rotational speed of the unit, the severing means moves out of the channel ahead of the core which is passing therethrough. The apertures or slots in the track may be obtained, for example, by providing a plurality of strips parallel to one another in the direction of advancement of the web material. The distance between the strips is sufficient to allow the passage of the severing means. In order to increase the versatility of the machine and simplify the construction of the web material severing means, in a preferred embodiment of the rewinder, the severing means are made in the form of pressers or pads (resilient, if required) which press against the surface of the first winder roller, or other material feeding means, to pinch the web material. Advantageously, to make the tearing of the web material easier, in the regions where the pressers act against the roller, the surface of the first winder roller may have a low coefficient of friction. To this end, the first winder roller may be provided with a surface having wide annular bands suitably polished, having a low coefficient of friction, and separated by narrow annular strips having a high coefficient of friction. This ensures the proper friction on the web to properly feed said web, in particular at the moment when the new core is rotationally accelerated. The annular strips with high coefficient of friction may be aligned with the strips which define the track or core rolling surface. With the arrangement above described, the length of the material wound into each individual log may be pre-determined and accurately controlled, regardless of the diameter or circumference of the first winder roller, inasmuch as there is no need for coordinating the position of the severing means with a particular portion of the surface of the winder roller, as is the case in the prior art machines. Similar results in terms of versatility are attained if the severing means are provided with blade portions (saw-toothed, if required) which cooperate with annular channels in the first winder roller. Blade means could operate with a longitudinal slot instead of annular channels. The unloading from the winder of a completed log or roll may take place by an accelerating third, diameter-control, roller disposed downstream of the first and second winder rollers, in a manner similar to that described in the above-mentioned GB-A-2,105,688. However, provision may also be made for the completed log to be unloaded by deceleration of the second winder roller, while keeping the peripheral speed of the third winder roller constant and substantially equal to the peripheral speed of the first winder roller. The deceleration of the second winder roller also causes the core to go through the nip defined by the first and second winder rollers. It is not excluded that the core passes through the nip between the first and second winder rollers by means of a small and constant difference in the peripheral speed between said two winder rollers. In this case, it may be necessary to provide a relative mobility of the first and second winder rollers. When provision is made for a deceleration of the second winder roller in order to unload the completed log and/or to allow the passage of the core through the nip, an actuator means may be provided which causes both the deceleration of said roller and the actuation of the web material severing means. This is possible because the latter will have to be operated only when a log has been completed and a new core has to be introduced, i.e., when the deceleration of the second winder roller is necessary. This greatly simplifies the structure of the machine. With the above and other objects in view, further information and a better understanding of the present invention may be achieved by referring to the following detailed description. Brief description of the drawings For the purpose of illustrating the invention, there is shown in the accompanying drawings a form thereof which is at present preferred, although it is to be understood that the various instrumentalities of which the invention consists can be variously arranged and organized, and that the invention is not limited to the precise arrangement and organizations of the instrumentalities as herein shown and described. In the drawings, wherein like reference characters indicate like parts: Fig. 1 shows a schematic side view of the rewinder according to the invention. Figs. 2 to 8 diagrammatically show successive working steps of the rewinder of Fig. 1. Fig. 9 shows a section taken on line IX-IX of Fig. 1. Figs. 10 and 11 show two embodiments of the web material severing means in a schematic side view. Fig. 12 shows a section taken on line XII-XII in Fig. 1 of one side frame on which the winder rollers and the severing means are supported, to illustrate the transmission for the actuation of the web material severing means and the deceleration of the second winder roller. Fig. 13 shows a modified embodiment of the invention wherein a belt is additionally combined to the first winder roller. Detailed description of preferred embodiment The basic elements of the rewinder will be described hereinafter by referring first to Fig. 1. Reference numerals 1 and 3 indicate rollers around which the web material N is fed from a supply parent roll (not shown) to the winding region of the rewinder. The web material N is fed through a perforation group, generally shown at 5, including a non-rotating support 7 and a rotating cylinder 9. The support 7 carries a counter-blade 11 which cooperates with blades 13 carried by the cylinder 9 to provide a line of perforations across the web. Located downstream of the perforation group 5 are a first winder roller 15, around which the web material is fed, and a second winder roller 17. In the illustrated example, the two rollers 15 and 17 each rotates in a counter-clockwise direction. The cylindrical surfaces of rollers 15 and 17 define a nip 19 through which the web material N is fed. Numeral 21 designates a third roller also rotating in a counter-clockwise direction and supported by an arm 23 pivoted at 25 to the machine frame. The arm 23 can oscillate to allow the roller 21 to be lifted and lowered by an actuator 27. The winder rollers 15, 17 and 21 define the region where the winding of each log is completed, according to the procedures to be described hereinafter. Located downstream of the three winder rollers is a chute 31 along which the completed logs L roll for the transfer thereof towards tail gluer means, not shown. Disposed upstream of the nip 19 is a curved surface or track 33 defined by a series of parallel arcuate strips 35 (Fig. 9) . The strips 35 have pointed ends 36 directed toward the nip 19 and which terminate in annular slots 37 of the lower winder roller 17. (See Figs. 10, 11 and 12). At the opposite end, the strips 35 terminate near the region at which the introduction of the cores A takes place, the latter being fed and inserted in the manner described hereinafter. The curved surface or track 33 and the cylindrical surface of the first winder roller 15 define a channel 39 for the passage of the cores A. The cross-section, i.e., the dimension of the channel 39 measured perpendicularly to the track 33, may be substantially uniform along the length of the strips and advantageously equal to, or slightly less than the diameter of the cores being used. This is achieved because the surface of the track 33 has a constant radius of curvature with its axis coincident with the axis of the winder roller 15. Arranged below the strips 35 which define the surface 33 is a rotary unit 41 carrying means 43, for the severance of the web material, which cooperate with the cylindrical surface of the winder roller 15. In this embodiment, the severing means includes pressers or pads 43 intended to exert a pressure, through a slight interference, against the surface of the roller 15. The unit 41 is made to rotate intermittently, in the illustrated example, in a clockwise direction. The pressers 43 move along a circular path C which has an axis coincident with the axis of rotation 45 of the unit 41 and almost tangent to (or making a slight interference with) the cylindrical surface of the winder roller 15. The cores are introduced into the channel 39 by means of a conveyor generally shown at 47 (see Fig. l) . The conveyor includes a flexible continuous member 49 made up, for example, of a chain or a belt driven around transmission wheels 51, 53, 55, one of which is motor-driven. Disposed at regular intervals on the flexible member 49 are pushers 57 each of which picks up a core from a container 59. The cores A are removed by the pushers 57 and lifted and transferred, through a gluing unit, generally shown at 61, which may include a tank 63 of glue in which a series of discs 65 rotate. Such gluers are well-known and need not be described in greater detail. In Fig. 1 only a few cores A are shown, but it is to be understood that, under proper operating conditions, a respective core A is carried by each pusher 57 from the container 59, across the wheel 51 to the wheel 55, close to the mouth of the channel 39, to start the winding of each log, as will be described hereinafter with reference to Figs. 2 to 8. Fig. 2 shows the final step of the winding of a log L. The first winder roller 15 and the third roller 21 rotate at a peripheral speed equal to the web material N feeding speed, while the second winder roller 17 rotates at a temporary lower peripheral speed to allow the completed log L to be moved towards the chute 31. At this stage, a new core Al has been brought by the relevant pusher 57 to the entrance of channel 39. The insertion of the core Al into the channel 39 may be carried out directly by the relevant pusher 57, or by an auxiliary pushing member, indicated by 67, rotating about the axis of wheel 55. The latter solution (shown in the illustrated example) allows the insertion of the core A to be performed with greater rapidity and precision, inasmuch as the insertion movement is unrelated to the movement of conveyor 47, the push member 67 being provided with an actuator which is independent of the actuator of the conveyor 47. During this stage, the rotary unit 41 rotates about its axis 45 and the pressers 43 have already entered the channel 39 by passing between the strips 35 which define the surface 33. The peripheral speed of pressers 43 is less than that of roller 15 and, therefore, also less than the speed of the web material N. In this way, the web material N is pressed between the two surfaces moving at different speeds. The effect of this difference in speed is a slowing down of the pinched portion with respect to - li ¬ the rest of the web material. This slowing down causes the web material to tear along the perforation line which is closest to the point at which the web material N is pinched. Fig. 3 shows the next stage in which the web material is torn off, giving rise to a new leading edge NL. The core Al has, in the meantime, started to rotate owing to the contact thereof with the stationary surface 33 and with the rotating cylindrical surface of the winder roller 15. The core moves forward (i.e., downstream), therefore, by rolling along surface 33 at a speed equal to half the feeding speed of the web material N. The cross dimension of channel 39, which is slightly less than the diameter of the core Al (the latter being typically made from pliable cardboard) , allows a friction to be generated. This friction is necessary for the angular acceleration of the core from zero to the rolling speed, and the adhesion of the web material N to the surface of said core, on which glue has been spread by the gluing device 61. The latter effect is missing when the gluing of the core is not provided. Fig. 4 shows the relative position taken by the core A and pressers 43 a few moments after severance of the web material N. The rotary unit 41 keeps on rotating at a speed lower than the web feeding speed, and also less than the advancing speed of core Al, so that a progressive approach of the core to the pressers 43 will take place. However, contact between core and pressers is avoided since a slight rotation of the rotary unit 41, causes the presser means move out of the channel 39 through the spaces between the strips 35. This allows the core Al to roll forward up to the nip 19 as shown in Fig. 5. In Fig. 5, the core has left the surface 33 and is in contact with the surfaces of the winder rollers 15 and 17 which, by rotating at slightly different speeds (roller 17 being slower) , cause the core to move forward through the nip 19. At the end of its advancement through the nip 19, the core will be located between the three rollers 15, 17 and 21, and the web material N will continue to wind up on the core, some turns thereof having already been wound during the transit of the core through the channel 39 and the nip 19. At this time the unit 41 keeps on rotating in clockwise direction until it reaches the position in Fig. 6 where it stops until the next operating cycle. Similarly, the auxiliary pushing member 67, which has continued to rotate simultaneously with the unit 41, is stopped at the angular position shown in Fig. 6. In this figure, the log L is shown in an intermediate winding step between the rollers 15, 17 and 21, the movable roller 21 being gradually moved upwards to allow the controlled increase of the log. Conversely, the conveyor 47 keeps on moving forward thus bringing the next core A2 to the inlet of channel 39, as can be seen in the next Fig. 7. The conveyor 47 may be provided with either continuous or intermittent motion, also in relation to the rewinder speed. In case the auxiliary pushing member 67 is not provided, the motion of the conveyor 47 should be in phase with that of the pressers 43 and the relevant rotating unit 41. Fig. 8 shows the almost completed log L, the core A2 being brought by the pusher 57 to the inlet of channel 39 and held in that position by a resilient retention finger 71. The latter prevents the core A2 from rolling down and coming in contact with the web material N before the rotary unit 41 is in place. As the rotary unit 41 and the auxiliary pushing member 67 are advanced, the system takes up the configuration shown in Fig. 8. As can be seen in this Figure, the auxiliary pushing member 67 is about to push the core A2 into the inlet of channel 39, and thus in contact with the web material N, and the pressers 43 are about to come in contact with the surface of the first winder roller 15. The next position is a repeat of the cycle as shown in Fig. 2.Figs. 2 to 8 illustrate the sequence of operations in which the contact between the new core Al and the web material N takes place an instant before the material N is torn off, and precisely the moment in which the contact between the pressers 43 and the material N begins. However, the contact between the core Al and the web material N may also be controlled to take place simultaneously with the tear, or with some delay. Tearing of the web material by pressers 43 is made easier by the fact that these are provided with a surface with high coefficient of friction, for example, made of rubber, while the corresponding regions of the roller 15 have a low coefficient of friction which facilitates the sliding of the web material on said roller. This arrangement may be as shown, in detail, in Fig. 9. In the annular regions 15A in which the contact of pressers 43 takes place, the roller 15 has a smooth surface. Said regions 15A are separated from one another by annular strips 15B having high coefficient of friction, disposed in alignment with the strips 35 and made up, for example, of emery cloth. This material is often employed on rollers to prevent the slipping of the web material. In this embodiment, since the regions 15A and 15B have annular development, it is possible to have the contact between the roller 15 and the pressers 43 at any point along the periphery of the roller 15. This allows the web material N to be severed at any moment, and thus an amount of web material N (accurately presettable independently of the circumferential development of the roller 5) to be wound on each log. Instead of presser means, such as those indicated by 43 in Figs. 1 to 8, severing means of different type may also be used. For example. Fig. 10 shows severing means 43 having sharp, saw-toothed blades 43A which cooperate with annular slots 15C provided in the surface of roller 15. The difference in speed between the blades 43A and the surface of the roller 15 causes the web material to tear. Also, in this case, there is no limitation between the angular position of the roller 15 and the position in which the severing means 43 operate. Fig. 11 shows, instead, a solution in which the blades 43A cooperate with a longitudinal (i.e., axial) slot 15D formed in the surface of roller 15. According to the difference in speed between the means 43 and the roller surface, the slot 15D is of a size which is sufficient to avoid interference between the two elements. Similarly to the embodiment of Fig. 10, this embodiment has the advantage of avoiding mutual mechanical contact between the severing means and the winder roller 15. However, in the embodiment of Fig. 10, a relation does exist between the angular position of the roller 15 and the position of the severing means 43, 43A. This imposes limits to the machine's versatility. In fact, the length of the web material wound on each log may vary only according to multiples of the circumference of roller 15, unless a mutual sliding between the web material N and the roller 15 is provided during winding of each log, with consequent cyclical rephasing of the position of the slot 15D and severing means 43, 43A. The embodiments of Figs. 10 and 11 are particularly suitable in case the rewinder has no perforation group 5. In this case, the rupture of the web material occurs where the serrated and/or sharpened blades are inserted. In the embodiments of Figs. 10 and 11, it is possible to operate the severing means at a peripheral speed equal to that of the web material, thereby reducing the width of channel 15D. In this case, the severance of the web material N is due to the incision thereof and not to a difference in speed. In case the web material is perforated (as by unit 5) , a synchronism must be suitably provided between the action of the severing means 43 and the position of the perforation line, so that the contact between the web material N and the severing means occurs in close proximity to a perforation line with the latter lying immediately downstream of the region of contact. To this end, provision may be made for a control unit, schematically shown at 2, to which data of angular position relative to the position of the cylinder 9 is supplied. The control unit 2 operates an actuator 75 which, as described hereinafter, controls the operation for the severance of the web material, as well as the insertion of the new core and the unloading of the log in synchronism with the position of the perforation line. The same control unit 2 may control the actuator 27 which moves the roller 21 up and down. Fig. 12 schematically shows a particularly advantageous example of the actuator and the drive means which control the motion of the web material severing means and core insertion means and the deceleration of the winder roller 17. In Fig. 12, numeral 73 indicates one of the machine's side frame which supports the second winder roller 17, the rotary unit 41, and the cylinder 68 which supports the auxiliary pushing member 67. Fig. 12 is a section taken on the line XII-XII of Fig. 1 from which the parts having no significant relation with the description of the means for the actuation of the rotary unit 41 have been taken away. Numeral 75 indicates a motor serving as actuator of the rotary unit 41. Keyed on the shaft 77 of motor 75 is a first toothed pulley 79 over which a toothed belt 81 is driven, the latter transmitting the motion to the rotary unit 41 via another pulley 83. A second toothed pulley 85, keyed on the shaft 77, transmits the motion, via a toothed belt 87, to a toothed pulley 89. The pulley 89 is keyed on a first input axle of a differential gear generally shown at 91. Fixed to the gear-holding case or box of the differential gear 91 is a pulley 93 on which a belt 95 is driven, the latter taking its motion from a machine member, not shown, rotating at a speed proportional to the feeding speed of the web material N. Said member may be any one of the web material-guiding and feeding rollers, such as the roller 15. Numeral 97 designates the output axle of the differential gear 91. Keyed on said output axle is a toothed pulley 99 which, through a toothed belt 101, transmits the motion to a toothed pulley 103 keyed on the shaft of the second winder roller 17. Also keyed on the rotary unit 41 is another pulley 105 which, through a belt 107, transmits the motion to a pulley 109 keyed on the shaft 68 which carries the auxiliary pushing member 67. In the winding stage of the log L between the rollers 15, 17 and 21 (i.e., in the stage shown in Figs. 6 and 7) , the motor 75 is at a standstill. The winder roller 17 is rotated directly by belt 95. The transmission ratio of the differential gear and of the pulleys is such as to achieve a peripheral speed of the roller 17 equal to the peripheral speed of the roller 15. When the winding of the log L is almost completed, the motor 75 is rotated. This has the effects of: (a) driving the rotary unit 41 which carries the severing means 43 into rotation; (b) driving the shaft 68 which supports the auxiliary pushing member 67 into rotation; and (c) modifying the transmission ratio between the pulley 93 and the winder roller 17 as a consequence of the rotation of the input axle of the differential 91. The modification of the transmission ratio between the pulley 93 and the roller 17 causes a deceleration of the latter and, therefore, a reduction of its peripheral speed with respect to the peripheral speed of roller 15. This deceleration is sufficient to unload the just-completed log L. Consequently, a single actuator (motor 75) makes it possible to operate the severance of the web material. the insertion of a new core and the discharge of a completed log, by use of an extremely simple and economical mechanism. However, different and independent actuators for the various members can be used. Provision may also be made for using a winder roller 17 rotating uniformly at a speed lower than that of roller 15 and for operating the discharge of the completed log L by accelerating the roller 21. This does not change the principle of the invention. When providing an acceleration of the roller 21, this may also have the effect of tensioning the web material N. By suitably phasing, for example, through the control unit 2, the acceleration of roller 21 with the actuation of the severing means 43, it is possible to pre-tension the web material before causing the tearing thereof by the contact between the means 43 and the roller 15. Fig. 13 shows a modified embodiment in which the channel 39 is not formed by the surface of a first winder roller, but by a separate web feeding means consisting of a plurality of belts 150 driven between a first winder roller 15, and an auxiliary cylinder 152, said belts being suitably spaced apart in the axial direction. Numeral 33 again indicates the surface defining, together with the belt system 150, a channel 39. The second and third winder rollers are again designated 17 and 21, respectively. Numeral 41 indicates the rotary unit carrying the severing means 43 which move through the slits between the strips 35 which define the surface 33. The core insertion means have been omitted in the drawing for the sake of clarity. Indicated by 154 is a surface which the belts 150 contact. The surface 154 may have a plurality of sliding seats for the belts 154, so that the severing means 43 (consisting of pressers or other means, as described above) act on an almost continuous transverse surface. The surface 54 may be made of a material having low coefficient of friction to facilitate both the sliding of the belts 152 and the tearing of the web material. The belts 152 are located in alignment with the strips 35 which define the surface 33, and the pressers 43 pass between adjacent belts 150. Also in this embodiment the interruption means may comprise blade means which cut the web material, in a similar way as provided by the means 43A. The speed of means 43, 43A may also be equal to the speed of the web material N, as the separation thereof is performed by a cutter (means 43A) or a counteracting stationary surface (154). It is understood that the drawings show an exemplification given only as a practical demonstration of the invention, as this may vary in the forms and dispositions without, nevertheless, coming out from the scope of the idea on which said invention is based. The possible presence of reference numbers in the appended claims has the purpose of facilitating the reading of the claims, reference being made to the description and the drawing, and does not limit the scope of the protection represented by the claims.

Claims: - 19 - CLAIMS 1. A rewinding machine for the formation of logs (L) of web material (N) wound on a core (A) , including: -a first winder roller (15) over which the web material is fed; -a second winder roller (17) defining, with the first winder roller, a nip (19) through which the core (A) and the web material (N) pass; -means (15; 150) for feeding the web material (N) into said nip (19) , which have an advancement speed substantially equal to the feeding speed of the web material (N) ; -insertion means (47; 57; 67) for introducing into said nip a core on which the web material is to be wound; -a web severing means (43; 43A) cooperating with said feeding means; characterized in that: -located upstream of said nip (19) , with respect to the web (N) feeding direction, is a surface (33) defining, together with the means (15; 150) for the feeding of the web material (N) , a channel (39) into which the core (A) is inserted; -said means (43; 43A) for severing the web material cooperates with said feeding means (15; 150) at an intermediate location along said channel, whereby to sever said web between the region of insertion of the new core and said nip (19) . 2. A rewinding machine according to Claim 1, characterized in that said means for feeding the web material (N) into the nip (19) consist of the cylindrical surface of the first winder roller (15) , and that the surface (33) defining said channel (39) is a curved surface. 3. A rewinding machine according to Claim 1, characterized in that said means for feeding the web material (N) into the nip (19) includes a conveyor system with flexible members (150) driven around the first winder roller (15) . 4. A rewinding machine according to Claim 2, characterized in that said surface (33) defining said channel (39) is a concave surface with a center of curvature coinciding with the center of rotation of the first winder roller (15) , the height of said channel (39) being equal to or slightly less than the diameter of the core. 5. A rewinding machine according to Claim 3, characterized in that associated to said flexible members (150) is a counteracting surface (154) . 6. A rewinding machine according to one or more of the preceding claims, characterized in that said surface (33) begins adjacent the point where the insertion means (67) releases the core and terminates near said nip (19) . 7. A rewinding machine according to one or more of the preceding claims, characterized in that: said severing means (43; 43A) move along a path (C) which is approximately tangent to said means for feeding the web material into the nip; and that, during the cooperation between the severing means and the feeding means, the feeding speed of the web material and that of the feeding means (15; 150) is greater than the peripheral speed of the severing means, the difference in speed creating a tensioning and thus a tearing of the web material between the formed log (L) and the region of contact between the web material and the severing means. 8. A rewinding machine according to one or more of claims 1 to 6, characterized in that: said severing means (43; 43A) move along a path (C) which is approximately tangent to the means for feeding the web material into the nip; that, during the cooperation between the severing means and the feeding means, the feeding speed of the web material (N) is approximately equal to the peripheral speed of the severing means, said severing means carrying blade members for the severance of the web material. 9. A rewinding machine according to one or more of the preceding claims, characterized in that said surface (33) defines with said feeding means (15; 150) a channel of almost uniform cross-section. 10. A rewinding machine according to one or more of the preceding claims, characterized in that said surface (33) has a terminal comb-like portion (36) with teeth which terminate in annular slots (37) in the surface of the second winder roller (17) . 11. A rewinding machine according to one or more of the preceding claims, characterized in that said surface (33) is defined by a plurality of strips (35) approximately parallel to one another extending in the web material feeding direction. 12. A rewinding machine according to Claim 11, characterized in that the first winder roller has, on its cylindrical surface, annular regions (158) with high coefficient of friction, disposed in alignment with the parallel strips (35) defining said surface (33). 13. A rewinding machine according to one or more of the preceding claims, characterized in that said severing means (43; 43A) are borne by a rotary unit (41) disposed outside said channel (39) defined by said surface (33), said severing means entering said channel through apertures in said surface (33) . 14. A rewinding machine according to one or more of the receding claims, characterized in that said severing means (43) include presser members (43) cooperating with the web feeding means. 15. A rewinding machine according to Claim 14, characterized in that said presser members (43) are resilient. 16. A rewinding machine according to Claim 14 or 15, characterized in that the surface of said presser members wich cooperates with said feeding means has high coefficient of friction. 17. A rewinding machine according to Claim 9, characterized in that said presser members (43) cooperate with surface portions of said feeding means (15; 150) having low coefficient of friction. 18. A rewinding machine according to one or more of claims 1 to 13, characterized in that said severing means are provided with blade elements (43A) cooperating with corresponding channels (15C; 15D) in the web feeding means (15; 150) . 19. A rewinding machine according to Claim 18, characterized in that said channels are annular channels (15C) . 20. A rewinding machine according to Claim 18, characterized in that said channels are longitudinal chapnels (15D) extending substantially parallel to the axis of the first winder roller (15) . 21. A rewinding machine according to one or more of the preceding claims, characterized by means (75, 91) for controlling the speed of the second winder roller, which keep the peripheral speed of the second winder roller (17) at a value less than the peripheral speed of the first winder roller (15) at least during the transit of the core through said nip (19) . 22. A rewinding machine according to Claim 21, characterized in that said speed control means (75, 91) cause a temporary deceleration of the second winder roller (17) to allow the transit of the core through said nip. 23. A rewinding machine according to Claim 22, characterized in that it includes an actuator means (75) for operating the severing means (43), which causes, simultaneously with the operation of the severing means, a temporary deceleration of the second winder roller. 24. A rewinding machine according to Claim 23, characterized in that associated with the second winder roller (17) is an epicyclic gear (91) provided with two inputs and one output, said output driving the second winder roller (17) into rotation, a first input (93) being connected to a transmission means (95) which has a motion proportional to the feeding speed of the web material (N) , and a second input (89) being connected to the actuator means (75) which operates the severing means (43; 43A) . 25. A rewinding machine according to one or more of the preceding claims, characterized in that it includes gluing means (61) which apply glue to the core prior to the insertion of the core into said channel (39) . 26. A rewinding machine according to Claim 25 characterized in that said gluing means are disposed along the path of the core (A) insertion means (47, 57, 67). 27. A rewinding machine according to one or more of the preceding claims, characterized in that said insertion means (47, 57, 67) include a container (59) and a conveyor (47) with a flexible continuous member (49) , carrying a plurality of pushers (57) which pick up the cores from said container (59) and convey them to the channel (39) , said flexible member (49) being curved as it passes the channel inlet. 28. A rewinding machine according to Claim 27, characterized in that each core (A) is inserted into the channel (39) directly by the respective pusher member (57). 29. A rewinding machine according to Claim 27, characterized in that associated to the flexible member is a retention finger (71) which retains the core prior to the insertion thereof into the channel (39) . 30. A rewinding machine according to Claim 27 or 29, characterized in that the insertion means further include an auxiliary pushing member (67) , moving at a speed independent of the pushers (57) to allow for a fast insertion of the core (A) into said channel (39) . 31. A rewinding machine according to one or more of the preceding claims, including a third winder roller (21) which is brought into contact with the outer surface of the log (L) in the course of formation and is gradually lifted to allow and control the increase of the diameter of said log (L) . 32. A rewinding machine according to Claim 31, characterized in that said third winder roller (21) rotates at a peripheral speed substantially equal to the peripheral speed of the first winder roller. 33. A rewinding machine according to Claim 31, characterized in that said third winder roller (21) is accelerated to unload the log (L) upon completion thereof. 34. A rewinding machine according to one or more of the preceding claims, characterized in that said surface (33) is substantially equi-distant from said feeding means (15; 150) along the entire length of the channel. 35. A method of producing logs (L) of web material (N) wound on a core (A) including the steps of: -providing a first winder roller and a second winder roller defining a nip between them for the transit of the web material and the core; -providing means for feeding the web material into said nip; -providing a web severing means cooperating with said means for feeding the web material into said nip; -feeding said web material (N) around said first winder roller; -providing a first core (A) and winding a predetermined amount of web material on said first core to form a log (L) ; -severing the web material to form a leading edge after having wound said predetermined amount of material on the first core (A) ; -introducing a second core (Al) , and winding thereon the said leading edge (NL) of the web material (N) formed after the severance; -causing the second core (Al) to move through said nip and thereafter completing the winding of a new log on said second core; characterized by: -providing a surface, upstream of said nip, which defines a channel in cooperation with the means for feeding the web material into said nip; -bringing said second core (Al) into contact with the web material (N) carried by said feeding means; -severing the web material by providing severing means between the region in which the second core contacts the web material and said nip; -causing the second core (Al) to roll along said channel and starting the winding of the web material therealong; and -causing said second core (Al) to move through said nip. 36. Method according to Claim 35, characterized by applying glue on said second core and making the leading edge of web material to adhere to said core by means of said glue.

Inventors: PERINI EVA, PERINI, EVA
Applicants: PERINI EVA, PERINI FABIO SPA, FABIO PERINI S.P.A., PERINI, EVA
Application year: 1994
Main classification: B65H19
IPC codes: B65H18, B65H19